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Why the Mets may have found a diamond in the rough in new pitcher Sean Manaea

Manaea flashed big upside with the Giants last year and could be a sneaky, low-cost addition to the back of New York’s rotation.

Sean Manaea of the San Francisco Giants pitches against the San Diego Padres at Oracle Park on September 27, 2023 in San Francisco, California. Photo by Lachlan Cunningham/Getty Images

While the baseball world waits to see how the rest of the top of the starting pitching market — your Blake Snells, Jordan Montgomerys, Shota Imanagas and Dylan Ceases — shakes itself out, the New York Mets went ahead with an under-the-radar signing that could look pretty shrewd in a few months’ time. Per Jon Heyman of the New York Post, the Mets have reached an agreement with former Athletics, Padres and Giants lefty Sean Manaea on a two-year, $28 million deal. The contract reportedly also includes an opt out after the 2024 season.

On the surface, it would seem to be hard for Mets fans to be too excited about this deal. Manaea pitched to a 4.44 ERA over 117.2 innings in 2023 (37 appearances, 10 starts), a figure that shakes out as just below league average (95 ERA+) when considering he played his home games in pitcher-friendly Oracle Park. An acceptable fifth starter for a team that doesn’t plan on contending in 2024, but nothing to write home about. But Manaea opted out of the $12.5 million he would’ve been owed by the Giants in 2024 for a reason — and there’s plenty of reason to believe he’s a rare undervalued free agent in a market short on quality pitchers.

For starters, that ERA starts to look a lot better when you drill down a bit. After a brutal start to the season — he posted a 7.96 mark over his first eight appearances, getting bumped from San Francisco’s rotation — Manaea went back to the drawing board, introducing a new sweeper to his arsenal. And from that point on, he was a whole new pitcher: The lefty posted a 3.60 ERA and 3.19 FIP from May 30 until the end of the season, striking out 84 batters in 85 innings across 26 appearances (four starts). Batters hit .140 with a .163 slugging percentage against the sweeper, with a healthy 35.1% whiff rate — a drastic improvemenet over his traditional slider (.285 BA, .567 SLG, 26.2% whiff rate). Unsurprisingly, the sweeper more or less replaced the traditional slider in the middle of the season and became Manaea’s go-to secondary pitch.

There’s also the velocity jump. With Oakland and San Diego, Manaea’s velocity was below average, sitting around 91 with his four-seam fastball. An offseason trip to the Driveline pitching lab, however, reworked his mechanics and unlocked a whole new heater. See for yourself:

Manaea added nearly 3 mph to his fastball in 2023, and he threw 34 of the 50 fastest pitches of his career last season. Of course, velocity isn’t everything, but it does give you greater margin for error, allowing a pitcher to get away with mistakes more often. In Manaea’s case, it also made his changeup more effective: Opponents hit .299 with a 529 slugging percentage against his changeup in 2022, marks that fell to .208 and .333, respectively, in 2023.

So you have a pitcher with plenty of starting experience who unlocked a far more formidable three-pitch arsenal last season, with the numbers to back it up. Manaea went from a 5.49 ERA in the first half to a 3.43 ERA in the second half, and he struck out 25.7% of the batters he faced — comfortably above the league average of 22.7% league average and matched Manaea’s career best in a full season. (He also set a new career low with a 36.4% hard-hit rate allowed, well below the league average of 39.2%.)

Does that mean that Manaea is guaranteed to pitch like an ace? Of course not; this is still a pretty high-risk profile. But there’s plenty of reason to believe that the lefty — who will turn 32 next month — can be an above-average starter in 2024 with a far lower commitment than the big names still on the market. That’s good news for this season’s Mets, who needed more arms behind Kodai Senga, Jose Quintana, Adrian Houser and Luis Severino. It’s also good for the franchise long-term: It’s not hard to see Manaea pitching well over the first half of the year and fetching a healthy return at the trade deadline, given his upside and his ability to fill a variety of roles on a contending team’s pitching staff. (Manaea’s 27 relief appearances in 2023 really ran the gamut, from bulk guy to closer to everything in between, and that means he can solve a whole bunch of different problems.)

It would’ve been nice for the Mets to earn a second year of commitment here, ensuring that Manaea will still be around when the team is really looking to ramp up in 2025. But that’s simply not the way the pitching market operates these days; there’s too much demand and too little supply for guys like Manaea to forfeit that much leverage. As it stands, this is among the shrewdest moves that new Mets president David Stearns could’ve made in his quest to fill out the team’s rotation this season, and a sign that his front office is evaluating well.